Thermoelectric generator for internal combustion engine



1965 E. c. KIEKHAEFER 3,

THERMOELECTRIC GENERATOR FOR INTERNAL COMBUSTION ENGINE Filed Sept. 28, 1962 2 Sheets-Sheet l 5O INVENTOR- ELMER C. K/EKHAEFER 7 FIG. 4 WWW 1965 E. c. KIEKHAEFER 3,217,695

THERMOELECTRIC GENERATOR FOR INTERNAL COMBUSTION ENGINE Filed Sept. 28, 1962 2 Sheets-Sheet 2 INVENTOR. Elm-R C. KIEKHAEFER jndrus Sfar/e Irma/vars be employed in connection with the motor.

United States Patent 3,217,696 THERMOELECTRIC GENERATUR FOR INTERNAL COMBUSTION ENGINE Elmer Carl Kielthaefer, Winter Haven, Fin assignor to Kiekhaefer Corporation, Fond du Lac, Wis, a corporation of Delaware Filed Sept. 28, 1962, Ser. No. 232,635 2 Claims. (Cl. 1232) This invention relates to an electric generator for an internal-combustion engine and is particularly directed to a thermo-electric generator in an outboard motor ernploying the heat of the engines exhaust gases to generate a current suitable for energizing the electrical system of the motor and auxiliary motor and boat accessories. This application is a continuation-in-part of applicants copending application entitled Electric Generator for Outboard Motors, Serial No. 777,926 which was filed December 3, 1958, now abandoned.

Outboard motors having an internal-combustion engine require an electrical ignition system which may include an electrically driven automatic starter. A storage battery is normally employed to energize the starting circuit. Running lights and other electrical accessories may also Auxiliary current generating units are provided supplying current to operate the motor and the electrical accessories and to maintain the charge on the storage battery.

Presently, the generators .are generally of the conventional electromagnetic variety and are mechanically connected to the engine for operation. The generator absorbs an appreciable amount of the power output of the motor and thus reduces the operating efficiency of the motor with respect to propulsion of the boat through the water.

Generators of present construction are also relatively bulky and interfere with modern compact and streamlined design of the motor.

In accordance with the present invention, a thermoelectric generator is mounted as a part of the internalcombustion engine with the hot junctions disposed directly in the path of the exhaust gases of the engine and the cold junctions disposed in the path of the engine cooling water.

In accordance with an aspect of the present invention, the thermoelectric generator of the present invention is a small, compact self-contained generator unit and one or more is clamped in place between the engine and the adjacent engine supporting surface or wall. The generator unit is located with the hot junction in the path of the exhaust gases emitted from the engine and the cold junctions are located within the cooling water inlet for the engine.

The relative positioning of the hot and cold junctions establishes a maximum temperature differential between the hot and cold junctions of the thermoelectric generator. The current and voltage output of the thermoelectric generator is determined by suitable series and parallel connections of thermocouple elements for connection in the motors electrical system.

Although the above mounting is a simple and inexpensive assembly, the area in which generators can be mounted is limited. In accordance with another aspect of this invention, one or more thermoelectric generators are mounted as a part of the internal engine wall separating the exhaust chamber adjacent the cylinders and the water cooling chamber. The generators may be conveniently mounted by press fitting within appropriate openings in the separating engine wall. This structure provides a very large working area and thus permits mounting of a substantial number of generators with the resultant increased electrical output.

Thermoelectric generators have a very substantial operating life and if properly protected will last the normal life of an internal-combustion engine. However, they are generally relatively fragile devices. The internal mounting of the generator in accordance with the present invention establishes a protective enclosure preventing accidental damaging thereof. The location of the hot junctions directly in the exhaust gases simplifies the mounting structure and cost because the heat is not transferred through an intermediate wall to which the generator must be secured.

The present invention takes the normally wasted heat energy in the exhaust gases and converts the heat energy into useful electrical energy. The necessity of absorbing a portion of the mechanical output of the motor is eliminated and maximum output of the motor is available to propel a boat through the water.

The thermoelectric generator provides an inexpensive and rugged electrical generating source for outboard motors.

The drawing furnished herewith illustrates the best mode presently contemplated for carrying out the invention.

In the drawing:

FIG. 1 is an elevational fragmentary view of an outboard motor and boat assembly with parts broken away and sectioned to show the cooling and the exhaust system of the motor;

FIG. 2 is a vertical cross-sectional view taken through a portion of FIG. 1;

FIG. 3 is an enlarged fragmentary view of the motor illustrating the mounting of the thermoelectric generator in FIG. 1;

FIG. 4 is a schematic circuit diagram of a thermoelec tric generator incorporated into the electrical system of an outboard motor;

FIG. 5 is a view similar to FIG. 2 illustrating another construction of the invention; and

FIG. 6 is a side elevational view of FIG. 5 with parts borken away.

Referring particularly to FIG. 1 of the drawing, an outboard motor 1 is secured to the aft end of a boat 2 and is adapted to propel the boat through a body of water, not shown. A storage battery 3 is disposed adjacent the aft end of the boat 2 and is connected into the electrical power system of the motor 1 by a releasable plug connection 4 in the front portion of motor 1. The plug connection 4 is of any suitable releasable variety having the motor mounted portion thereof connected to the boat and motor ignition starting and running system 5, schematically shown in FIG. 4. A thermoelectric generator 6 is mounted within the outboard motor 1 to establish a source of current to charge the battery 3 and provide electrical power to the electrical system 5.

The outboard motor 1 generally comprises an upper powerhead assembly 7 having an outer shell which houses an operating gasoline engine 8 and the various electrically operating engine components, not shown in FIGS 1-3.

The upper powerhead assembly '7 is secured to a hollow drive shaft housing 9 which extends downwardly and terminates in a separable gear casing 10.

The illustrated engine 8 is any suitable internal-combustion engine and conventionally is a two-cycle or fourcycle gasoline engine of the multi-cylinder variety which is adapted to establish sufficient power output for driving the boat 2.

The illustrated engine 8 comprises a cylinder block 11 formed from a suitable light-weight alloy and having a series of four vertically stacked cylinders 12. A piston 13 is slidably journaled within each of the cylinders 12 and is secured to a vertically disposed crankshaft 14. The pistons are reciprocated in the conventional manner by suitable gasoline explosions in the outer portion of the cylinder to rotate the crankshaft 14.

A drive shaft 15 is secured to the lower end of crankshaft 14 by a suitable coupling 16 and extends vertically through the drive shaft housing 9 and into the gear casing 1%. The lower end of drive shaft 15 is connected by a suitable gear mechanism 17 to drive a propeller 18 which is rotatably journaled within the gear casing 10.

Referring particularly to FIG. 2, the cylinders 12 are provided with individual air intake passages 19 to supply combustion air into the cylinder. Individual exhaust ports 20 are formed in the cylinders 12 diametrically opposite from the air intake openings 19 to allow the exhause gases to pass out of the cylinder after the explosion or firing of the mixture of the gas and admitted air. The end and side walls 21 of the cylinder block 11 adjacent the exhaust ports 20 extend laterally outwardly to form a recess immediately adjacent the exhaust ports. A manifold baffle plate 22 is bolted or otherwise secured about the outer edge of the extended walls 21 and establishes an expansion chamber 23 into which the exhaust gases are initially discharged.

The enlarged expansion chamber 23 allows the exhaust gases to expand and reduce the danger of a back pressure being built up adjacent the exhaust ports 20 which would interfere with the complete expulsion of the exhaust gases from the cylinder.

A discharge exhaust opening 24 is integrally cast into the lower portion of the engine block 11 in communication with the expansion chamber 23 and the hollow drive shaft housing 9 to direct the gases outwardly of the chamber. The housing 9 constitutes a vertical exhaust passage 25 which extends downwardly to the lower gear casing 10. The lower end of the drive shaft housing 9 and the adjacent upper end of the gear casing 10 are extended rearwardly as at 26 to direct the exhaust gases rearwardly of the propeller 18. A discharge spout 27 is secured to the under surface of the extended portion 26 of gear casing 10 rearwardly of the propeller 18 and correspondingly discharges the gases into the water.

The illustrated engine 8 is water cooled to carry away the heat generated by the successive explosions within the gasoline engine. Referring particularly to FIG. 2, the illustrated cylinder block 11 is cast with a continuous water cooling jacket 28 encircling the upper portions of the individual cylinders 11 of the engine 8. A water inlet passage 29 is integrally cast in the lower portion of the cylinder block 11 in communication with the water jacket 28 immediately adjacent the exhaust passage or opening 24. The water from inlet passage 29 passes upwardly through the cooling jacket 28 to a discharge passage 30 in the upper end of the cylinder block 11. The discharge passage 30 is connected to cooling chambers 31 and 32 on opposite sides of cylinder block 11 to cool the exhaust gases and to further cool the engine block 11.

The cooling chamber 31 is formed by a slightly cupshaped manifold cover 33 which is hermetically sealed to the cylinder block 11 over the manifold baffie plate 22. An opening 34 in baflie plate 22 is aligned with the discharge passage 30 to directly connect the water jacket 28 with the upper end of cooling chamber 31. The cooling water passes downwardly through the cooling chamber 31 and serves to cool the exhaust gases in the adjacent chamber 23. A discharge port 35 is provided in the lower portion of the cylinder block 11 in alignment with an opening in baffle plate 22 and connects the lower portion of the water cooling chamber 31 to the exhaust passage 25 defined by the hollow drive shaft housing 9. The cooling water from chamber 31 thus mixes with the exhaust gases to further cool the gases and is also discharged through the spout 27 The cooling chamber 32 is formed by securing a cover 36 to laterally extended side walls of the opposite side of the cylinder block 11. A bridging passage 37 in the upper portion of the cylinder block connects the cooling chamber 32 to the cooling chamber 31 such that a portion of the water flowing into the cooling chamber 31 bypasses into the cooling chamber 32. A discharge port 38 for chamber 32 is provided in the lower portion of the cylinder block 11 and terminates in communication with the exhaust passage 25 defined by hollow drive shaft housing 9. The cooling water from chamber 32 also discharges with the exhaust gases to further reduce the temperature of the gases.

Fresh water is continuously delivered to water packet 28 and then to cooling chambers 31 and 32 by a water pump 39 in the gear casing 10. A connecting tube 40 is secured to the water inlet passage 29 in the cylinder block 11 at its upper end and extends downwardly to the output of a water pump 39. An input conduit 41 is connected to the pump 39 and to a Water inlet passage 42 overlying the propeller 18. The pump 39 is coupled to the drive shaft 15 and operates in synchronism therewith. The output of the water pump 39 consequently varies directly in accordance with the rotation of the drive shaft and establishes cooling of the engine 8 generally in accordance with the speed of the engine 8 and the rate of heat generation.

Generally, the exhaust gases are at a very high temperature when they are expelled from a cylinder 11. The heat energy is displaced in the cooling water in the jacket 28 and chamber 31 and discharged to the fresh water through the exhaust passage 25 and discharge spout 27. The immediate cooling of the exhaust gases by air or water cooling is normally required to reduce the danger of establishing high back pressures at the exhaust ports and thereby insures the expulsion of the remaining exhaust gases from the combustion cylinder before the piston closes off the exhaust ports.

However, the exhaust gases remain at a relatively high temperature and the heat energy is normally completely lost. In accordance with the present invention, this byproduct heat energy is employed to operate the thermoelectric generator 6.

Referring particularly to FIGS. 1 and 3, the illustrated thermoelectric generator 6 includes an outer tubular housing 43 having opposite ends of the housing constituting the hot and cold junction ends 44 and 45 respectively. The thermoelectric generator 6 is mounted within a horizontal opening formed by semi-cylindrical recesses in the lower mating surface of cylinder block 11 and the adjacent bottom wall portion 46 of the powerhead assembly housing 7 between the exhaust opening 24 and the water inlet opening 29. The generator 6 is clamped in operating position by the cooperating wall with the hot junction end 44 in the discharge exhaust opening and the cold junction end in the water inlet opening 29.

The hot junction end 44 is thus mounted directly in the path of the exhaust gases from the expansion chamber and the cold junction end 45 is disposed within the cooling liquid as it enters the cylinder water jacket 28. This establishes a very high temperature differential as the exhaust gases are only partially cooled and the cooling Water is essentially at the cold pickup temperature.

As more fully described hereinafter, the temperature differential at the opposite end of the thermoelectric generator 6 causes a current to be generated within the thermoelectricgenerator. A pair of output leads 47 and 48 extend from the generator 6 to carry the current to the motors electrical system. The lead 47 is grounded to the motor in common with one side of the various electrical load components as schematically shown in FIG. 4. The lead 48 extends beneath the lower part of the upper power head assembly 7 within the drive shaft housing 9, then upwardly into the powerhead assembly through an opening 49 which is provided in the lower end of the power head assembly. The lead 43 is connected in the electrical system of the engine 8 and other accessories, as schematically shown in FIG. 4.

Referring particularly to FIG. 4, the storage battery 3 is connected by the releasable plug connection 4 to an outboard motor circuit which for purposes of illustration includes a solenoid and starter 58, a distributor 51 and running lights 52. A starting switch 53 is mounted on the boat 2 adjacent the motor 1 and connected in series with one side of the starter 50.

In accordance with the present invention, the thermoelectric generator 6 provides an auxiliary source of current to maintain the charge on battery 3 and to supply current directly to the electrical components as follows.

Referring particularly to FIG. 4, the thermoelectric generator 6 is illustrated as including parallel connected thermopiles 54 and 55. Each thermopile 54 and 55 includes a length of wire consisting of alternate lengths of dissimilar metals 56 and 57 which are successively joined by physical contact junctions 58 and 59 to form a series of thermocouples.

The application of heat to alternate junctions establishes a current flow across the junction due to the characteristics of metals. The current flow for any two given dissimilar metals is always from the one type metal to the other. Consequently, only alternate junctions are heated to avoid cancellation of the currents or voltages in the adjacent junctions. Further, by cooling the unheated junction, the opposed currents or voltages are further reduced and the net current flow is increased.

The dissimilar metals 56 and 57 may be any suitable variety. Thus, known pairs of dissimilar metals which are commercially employed in thermopiles are constantan and copper wire or chromel and aluminum.

The thermopile wire is folded back and forth at the physical contact junctions to group corresponding alternate junctions and establish a group of hot junctions 58 at one end and a group of cold junctions 59 at the opposite end for ready heating and cooling of the respective junctions.

The wire is insulated and the thermocouples 54 and 55 are bundled into a tubular configuration and disposed within the housing 43 with the hot junctions 58 at the hot end 44 and the cold junctions 59 at cold end 45 of the thermoelectric generator 6.

The current output is dependent in part upon the temperature differential between the hot junctions 58 and the cold junctions 59. The generator housing 43 is preferably formed from a heat resistant material to minimize the transfer of heat between the hot and cold junctions 58 and 59 of the thermopiles 54 and 55 and consequently maintain maximum temperature differential between hot and cold junctions.

Referring to the illustrated circuit in FIG. 4, the thermopiles 54 and 55 are connected in parallel to increase the current output at a preselected voltage corresponding to the voltage of the battery 3 and the load components. The number of thermocouples series connected within each thermopile 54 and 55 controls the maximum voltage output of the generator 6. The thermopiles 54 and 55 are direct current output devices and are therefore suitable for direct connection in the electrical circuit of the engine 8.

One side of the thermopiles 54 and 55 is grounded to the motor 1 by the common lead 47 and the opposite side is connected to the ungrounded side of the electrical circuit by the lead 48 in accordance with the polarity of the battery 3.

In accordance with the illustrated embodiment of the present invention, a half-wave rectifier 60 is suitably mounted within the powerhead shell 7 and is connected in series with the ungrounded lead 48. The rectifier 60 is polarized with respect to battery 3 to allow current flow only from the thermoelectric generator 6 to the battery 3 and to block all current flow from the battery to the thermoelectric generator 6. The rectifier 66 thus prevents discharging of the battery 3 when the voltage output of the thermoelectric generator 6 is lower than the battery voltage.

The rectifier 66 is preferably a solid state rectifying device because they are small, rugged and long life as well as relatively inexpensive. Selenium rectifier plate type and silicon or germanium wafer type units are readily available commercially and may be employed in the present circuit.

The operation of the illustrated embodiment of the invention is summarized as follows.

The motor 1 is mounted on the boat 2 and connected to the battery 3. The start button 53 is actuated to apply the output of the battery 3 to the electric starter 50. The operation of the motor 1 generates the exhaust gases which are discharged through the exhaust chamber 23 and passages 24-26, as previously described. The operation of the motor 1 also establishes circulating flow of cooling fluid from pump 39 and through the cooling chambers 31 and 32, as previously described.

The high temperature exhaust gases pass over the hot junction end 44 of the generator 6 and the incoming cooling water passes over the cold junction end 45 of the generator 6. A relatively great temperature differential is consequently established between the hot junctions 58 and the cold junctions 59 of the thermopiles 54 and 55. Consequently, a suflicient current is generated to supply the necessary power to the distributor 51 and the light 52 and other components of the motor 1 and boat 2 and to maintain the charge in the battery 3.

The current output of the thermoelectric 6 is dependent upon a number of variables which can be readily determined in designing a generator for any particular outboard motor design. For example, the number of parallel and series thermocouple junctions employed, the size of the physical junctions, the particular dissimilar metals employed and the temperature differential between the hot and cold junctions as determined by the temperature of the exhaust gases and cooling liquid are considered in designing a generator 6.

The location of the thermoelectric generator 6 immediately adjacent the exhausting discharge gases and the immediately incoming water provides a substantial temperature differential which in normal operation provides sufficient power output for operating the motor 1 and boat 2 without discharging of the battery 3. If increased output is required, more than one generator can be provided.

The rectifier 66 serves as a one-way switch and prevents discharge of the battery 3 through the thermoelectric generator 6 when the motor is not operating or the voltage output of the thermoelectric generator 6 is less than the voltage of the battery.

Although the clamping recess for generator 6 is shown defined by grooves in the adjoining surfaces of block 11 and wall portion 46 of the powerhead assembly housing 7, the recess may be formed in one of the members with the opposite member forming a closure having a flat surface. Further, if sutficient area is provided, the generator may be press fitted or otherwise secured within an appropriate opening although the clamped mounting is a superior practical construction.

Referring particularly to FIGS. 5 and 6, an alternative construction is shown with an engine structure corresponding essentially to that of FIGS. 1 and 2 and the corresponding components are similarly numbered for simplicity and clarity of explanation.

In FIGS. 5 and 6, the exhaust expansion chamber 23 and cooling chamber 31 of engine 8 are separated by a manifold baffle plate 61. A plurality of thermoelectric generators 62, corresponding to generator 6 of FIGS. 1-4, are press fitted or otherwise suitably secured within corresponding openings 63 in bafile plate 61. The cold junction end 64 of each generator 62 is located within the cooling chamber 31 and the hot junction end 65 of each is located within the expansion chamber 23. The baffle plate 61 provides a very substantial area in which generators 62 may be readily mounted in a protected manner.

In operation, the extremely hot exhaust gases from the cylinders 12 pass into the expansion chamber to heat the hot junctions. The cold junctions are cooled by the water flowing through cooling chamber 31. Although the water in chamber 31 has been heated in passing through cooling jacket 28 around cylinder 12, the temperature is far below that of the hot exhaust gases in expansion chamber 23 such that the generators 62 produces a current output. The plurality of generators 62 can therefore readily provide the necessary or desired output.

The thermoelectric generator is free of all moving components and is relatively low in initial cost. The elimination of all moving parts in the generator system for the engine essentially eliminates the maintenance costs. The internal mounting of the generator is relatively simple and inexpensive and provides a protective enclosure for the generator.

The generator of this invention can also be employed as an auxiliary current source to reduce the load on a conventional generator in an outboard motor and the like.

The present invention thus provides a relatively rugged and inexpensive generator for outboard motors and the like which increases the overall efi'iciency of the outboard motor by converting waste heat energy into useful electrical energy.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. In an internal combustion engine, a water-cooled engine block, a first cooling chamber adjacent an explosion chamber for cooling the walls thereof and having an exhaust gas expansion chamber connected to the explosive chamber, said expansion chamber having an outer wall, a tubular thermoelectric generator having a hot junction end and a cold junction end, means securing the gen- 4 erator in sealing engagement within an opening in said outer wall with the hot junction end disposed within the expansion chamber and the cold junction end disposed outwardly of the outer wall, and an exterior cup-shaped wall structure releasably secured to the engine block coextensively with the outer wall of the expansion chamber and defining a second cooling chamber for cooling said gases and simultaneously cooling said cold junctions, said second cooling chamber being connected to receive water from the first cooling chamber.

2. In an outboard motor having a water cooled internalcombustion engine, an engine block having a water cooling passageway for cooling the engine with an inlet opening terminating within a lower wall of the engine block, said engine block having an exhaust chamber and passageway for exhausting hot gases with an exhaust discharge opening in said lower wall spaced from said inlet opening, a mounting frame having an upper wall, means mounting said engine block with the lower wall abutting said upper wall, said upper wall including passageways aligned with said inlet opening and said exhaust discharge opening, at least one of said walls having a recess in the abutting surface and defining a tubular transverse passageway between the exhaust passageway and the cooling passageway, and a tubular thermoelectric generator clamped within said recess to close said transverse passageway with the hot junctions disposed in the exhaust passageway and the cold junctions in the cooling passageway.

References Cited by the Examiner UNITED STATES PATENTS 1,118,269 11/1914 Creveling 136-4111 1,134,452 4/1915 Hale 1354.1 1,242,499 10/1917 Webb 136-4.111 1,286,429 12/1918 Shindel 136-412 1,707,897 4/1929 Bizet 123-51 2,909,03 1 10/ 1959 Kiekhaefer -3l FOREIGN PATENTS 353,252 4/ 1905 France. 839,846 4/1939 France.

WINSTON A. DOUGLAS, Primary Examiner.

JOHN H. MACK, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Not 3,217,696 November 16, 1965 Elmer Carl Kiekhaefer It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

line 13, for "packet" read jacket line 2f Column 4 line 11, for

for "displaced" read dissipated column "produces" read produce Signed and sealed this 2nd day of August l966 (SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Qommissioner of Patents 

1. IN AN INTERNAL COMBUSTION ENGINE, A WATER-COOLED ENGINE BLOCK, A FIRST CHAMBER ADJACENT AN EXPLOSION CHAMBER FOR COOLING THE WALLS THEREOF AND HAVING AN EXHAUST GAS EXPANSION CHAMBER CONNECTED TO THE EXPLOSIVE CHAMBER, SAID EXPANSION CHAMBER HAVING AN OUTER WALL, A TUBULAR THERMOELECTRIC GENERATOR HAVING A HOT JUNCTION END AND A COLD JUNCTION END, MEANS SECURING THE GENERATOR IN SEALING ENGAGEMENT WITH AN OPENING IN SAID OUTER WALL WITH THE HOT JUNCTION END DISPOSED WITHIN THE EXPANSION CHAMBER AND THE COLD JUNCTION END DISPOSED OUTWARDLY OF THE OUTER WALL, AND AN EXTERIOR CUP-SHAPED WALL STRUCTURE RELEASABLY SECURED TO THE ENGINE BLOCK COEXTENSIVELY WITH THE OUTER WALL OF THE EXPANSION CHAMBER AND DEFINING A SECOND COOLING CHAMBER FOR COOLING SAID GASES AND SIMULTANEOUSLY COOLING SAID COLD JUNCTIONS, SAID SECOND COOLING CHAMBER BEING CONNECTED TO RECEIVE WATER FROM THE FIRST COOLING CHAMBER. 